Correct, but worth qualifying.
The original first fit engine, Packard or Rolls Royce built, determines the mark number specified on the build documentation and A.M. movement card.
An original build Mk XVI subsequently fitted with a RR Merlin in latter years, post RAF service, is still a Mk XVI in my book.
Mark
Any news on vol.2 of the book? Or is it worth to wait for the results of the Burma excavations?